Ecotoxicological impacts of surface water and wastewater from conventional and advanced treatment technologies on brood size, larval length, and cytochrome P450 (35A3) expression in Caenorhabditis elegans

Emerging pollutants in the aquatic environments: A review of genotoxic impacts

Urbanization and industrial growth have negatively impacted water quality, raising concerns about emerging aquatic pollutants. Despite advancements in water treatment, these substances persist, endangering aquatic life and human health. Although research has focused on the physiological effects of these pollutants, their genetic damage potential remains poorly understood. This systematic review aimed to consolidate existing knowledge on the genotoxic potential of emerging aquatic pollutants. A comprehensive search was conducted across major databases, encompassing articles published from 2001 to 2022. The review primarily focused on research articles that evaluated genotoxicity in environmental samples containing emerging pollutants, as well as in vitro studies using various concentrations of these substances. Fourteen articles were included in the review, with pharmaceutical compounds, personal care products, disinfection byproducts, and industrial chemicals being the most extensively investigated classes. Other notable pollutants included metals, cyanotoxins, antiseptics, pesticides, and caffeine. All these pollutants classes were found to cause DNA damage, either in vitro at specific concentrations or in complex environmental mixtures. The comet assay was the most frequently used method, owing to its sensitivity and practicality in assessing DNA damage. For some pollutants, different responses were observed when comparing in vitro and in vivo studies, emphasizing the need for studies employing both approaches. However, the limited number of available articles underscores the necessity for further research on the genotoxic potential of emerging pollutants. More research is required to clarify mutagenicity, DNA repair kinetics, and cumulative effects of pollutants, which are critical for shaping policies and ensuring safe water quality. A greater knowledge about these pollutants will enable better understanding risk mitigation, ultimately protecting public health and ecosystems.

Proso millet peroxidase-mediated degradation and detoxification of Rhodamine B in water

Enzymatic catalysis is a promising approach for the degradation of organic pollutants and peroxidases (PODs) are one of the most common enzyme classes used to degrade organic pollutants. Proso millet peroxidase (PmPOD) is a peroxidase extracted and purified from proso millet bran which is the by-product of proso millet processing. In this study, we investigated the effects of PmPOD on the degradation of typical organic pollutants (Rhodamine B (RhB), bisphenol A, sulfadiazine) for the first time. Moreover, we screened RhB as the substrate with the best degradation effect. The degradation rate of RhB catalyzed by PmPOD (10 nM) reached 99.46% in 30 min under the optimal conditions (pH 5, 30°C, and molar ratio of RhB, H2O2 and HOBT of 1:9.58:1.94 × 10-3). The reaction kinetics parameters of PmPOD-mediated RhB degradation Km, Vmax and kcat were 62.2, 935.7 and 9.357 × 104, respectively. High-performance liquid chromatography analyses confirmed that PmPOD transformed RhB into two new products. Furthermore, toxicological evaluation in Caenorhabditis elegans demonstrated that 10 μg/mL RhB significantly reduced the lifespan by 8.3%, reduced the motility and pharynx-pumping rate compared with the control group, while the 10 μg/mL RhB product had no significant effect on these indexes. These data indicated that the toxicity of RhB disappeared after catalytic degradation by PmPOD. Taken together, these data suggest that catalysis of PmPOD is an effective method for degradation and detoxification of RhB. This study provides a potential candidate method for the biological treatment of RhB, and improves the added value of proso millet bran.

Caenorhabditis elegans as a suitable model to evaluate the toxicity of water from Rolante River, southern Brazil

Urbanization and agricultural activities increased environmental contaminants. Integrated analysis of water parameters and bioassays represents an essential approach to evaluating aquatic resource quality. This study aimed to assess water quality by microbiological and physicochemical parameters as well as the toxicological effects of water samples on the Ames test and Caenorhabditis elegans model. Samples were collected during (collection 1) and after (collection 2) pesticide application in the upper (S1), middle (S2), and lower (S3) sections of the Rolante River, southern Brazil. Metals were determined by GFAAS and pesticides by UPLC-MS/MS. Bioassays using the Ames test and the nematode C. elegans were performed. Levels of microbiological parameters, as well as Mn and Cu were higher than the maximum allowed limits established by legislation in collection 2 compared to collection 1. The presence of pesticide was observed in both collections; higher levels were found in collection 1. No mutagenic effect was detected. Significant inhibition of body length of C. elegans was found in collection 1 at S2 (P < 0.001) and S3 (P < 0.001) and in collection 2 at S2 (P = 0.004). Comparing the same sampling site between collections, a significant difference was found between the site of collection (F(3,6)=8.75, P = 0.01) and the time of collection (F(1,2)=28.61, P = 0.03), for the S2 and S3 samples. C. elegans model was useful for assessing surface water quality/toxicity. Results suggest that an integrated analysis for the surface water status could be beneficial for future approaches.

Survival of Nematode Larvae Strongyloides papillosus and Haemonchus contortus under the Influence of Various Groups of Organic Compounds

Many chemically synthesized xenobiotics can significantly inhibit the vitality of parasitic nematodes. However, there is yet too little research on the toxicity of such contaminating compounds toward nematodes. Compounds that are present in plants are able to inhibit the vitality of parasitic organisms as well. According to the results of our laboratory studies of toxicity, the following xenobiotics caused no decrease in the vitality of the larvae of Strongyloides papillosus and Haemonchus contortus: methanol, propan-2-ol, propylene glycol-1,2, octadecanol-1, 4-methyl-2-pen-tanol, 2-ethoxyethanol, butyl glycol, 2-pentanone, cyclopentanol, ortho-dimethylbenzene, dibutyl phthalate, succinic anhydride, 2-methylfuran, 2-methyl-5-nitroimidazole. Strong toxicity towards the nematode larvae was exerted by glutaraldehyde, 1,4-diethyl 2-methyl-3-oxobutanedioate, hexylamine, diethyl malonate, allyl acetoacetate, tert butyl carboxylic acid, butyl acrylate, 3-methyl-2-butanone, isobutyraldehyde, methyl acetoacetate, ethyl acetoacetate, ethyl pyruvate, 3-methylbutanal, cyclohexanol, cyclooctanone, phenol, pyrocatechin, resorcinol, naphthol-2, phenyl ether, piperonyl alcohol, 3-furoic acid, maleic anhydrid, 5-methylfurfural, thioacetic acid, butan-1-amine, dimethylformamide, 1-phenylethan-1-amine, 3-aminobenzoic acid. Widespread natural compounds (phytol, 3-hydroxy-2-butanone, maleic acid, oleic acid, hydroquinone, gallic acid-1-hydrate, taurine, 6-aminocaproic acid, glutamic acid, carnitine, ornithine monohydrochloride) had no negative effect on the larvae of S. papillosus and H. contortus. A powerful decrease in the vitality of nematode larvae was produced by 3,7-dimethyl-6-octenoic acid, isovaleric acid, glycolic acid, 2-oxopentanedioic acid, 2-methylbutanoic acid, anisole, 4-hydroxy-3-methoxybenzyl alcohol, furfuryl alcohol. The results of our studies allow us to consider 28 of the 62 compounds we studied as promising for further research on anti-nematode activity in manufacturing conditions.

Effects of conventionally treated and ozonated wastewater on the damselfly larva oxylipidome in response to on-site exposure

Pharmaceutical residues discharged through insufficiently treated or untreated wastewater enter aquatic environments, where they may adversely impact organisms such as aquatic invertebrates. Ozonation, an advanced wastewater treatment technique, has been successfully implemented to enhance the removal of a broad range of pharmaceuticals, however diverse byproducts and transformation products that are formed during the ozonation process make it difficult to predict how ozonated wastewater may affect aquatic biota. The aim of this study was to investigate effects on fatty acid metabolites, oxylipins, in a common invertebrate species, damselfly larvae, after on-site exposure to conventional wastewater treatment plant (WWTP) effluent and additionally ozonated effluent at a full-scale WWTP. Subsequent ozonation of the conventionally treated wastewater was assessed in terms of i) removal of pharmaceuticals and ii) potential sub-lethal effects on the oxylipidome. Northern damselfly (Coenagrion hastulatum) larvae were exposed for six days in the treatment plant facility to either conventional WWTP effluent or ozonated effluent and the effects on pharmaceutical levels and oxylipin levels were compared with those from tap water control exposure. Ozonation removed pharmaceuticals at an average removal efficiency of 67% (ozone dose of 0.49 g O₃/g DOC). Of 38 pharmaceuticals detected in the effluent, 16 were removed to levels below the limit of quantification by ozonation. Levels of two oxylipins, 12(13)-EpODE and 15(16)-EpODE, were reduced in larvae exposed to the conventionally treated wastewater in comparison to the tap water control. 15(16)-EpODE was reduced in the larvae exposed to ozonated effluent in comparison to the tap water control. One oxylipin, 8-HETE, was significantly lower in larvae exposed to conventional WWTP effluent compared to ozonated effluent. In conclusion, the study provides proof-of-principle that damselfly larvae can be used on-site to test the impact of differentially treated wastewater.

Effects of benzo(a)pyrene on meiobenthic assemblage and biochemical biomarkers in an Oncholaimus campylocercoides (Nematoda) microcosm

A microcosm experiment was carried out to determine how benzo(a)pyrene (BaP) may affect marine meiofauna community, with a main emphasis on nematode structure and functional traits. Three increasing concentrations of BaP (i.e. 100, 200 and 300 ng/l, respectively) were used for 30 days. The results revealed a gradual decrease in the abundance of all meiobenthic groups (i.e. nematodes, copepods, amphipods, polychaetes and oligochaetes), except for isopods. Starting at concentrations of 200 and 300 ng/l BaP, respectively, significant changes were observed at community level. At taxonomic level, the nematode communities were dominated at the start of the experiment and also after being exposed or not to BaP by Odontophora villoti, explicable through its high ecologic ubiquity and the presence of well-developed chemosensory organs (i.e. amphids), which potentially increased the avoidance reaction following exposure to this hydrocarbon. Moreover, changes in the activity of several biochemical biomarkers (i.e. catalase 'CAT', gluthatione S-transferase 'GST', and ethoxyresorufin-O-deethylase 'EROD') were observed in the nematode species Oncholaimus campylocercoides, paralleled by significant decreases in CAT activity for non-gravid females compared to controls at concentrations of 25 ng/l BaP and associated with significant increase in GST and EROD activities for both types of individuals.

Planococcus maritimus ML1206 Isolated from Wild Oysters Enhances the Survival of Caenorhabditis elegans against Vibrio anguillarum

With the widespread occurrence of aquaculture diseases and the broad application of antibiotics, drug-resistant pathogens have increasingly affected aquatic animals’ health. Marine probiotics, which live under high pressure in a saltwater environment, show high potential as a substitute for antibiotics in the field of aquatic disease control. In this study, twenty strains of non-hemolytic bacteria were isolated from the intestine of wild oysters and perch, and a model of Caenorhabditis elegans infected by Vibrio anguillarum was established. Based on the model, ML1206, which showed a 99% similarity of 16S rRNA sequence to Planococcus maritimus, was selected as a potential marine probiotic, with strong antibacterial capabilities and great acid and bile salt tolerance, to protect Caenorhabditis elegans from being damaged by Vibrio anguillarum. Combined with plate counting and transmission electron microscopy, it was found that strain ML1206 could significantly inhibit Vibrio anguillarum colonization in the intestinal tract of Caenorhabditis elegans. Acute oral toxicity tests in mice showed that ML1206 was safe and non-toxic. The real-time qPCR results showed a higher expression level of genes related to the antibacterial peptide (ilys-3) and detoxification (ugt-22, cyp-35A3, and cyp-14A3) in the group of Caenorhabditis elegans protected by ML1206 compared to the control group. It is speculated that ML1206, as a potential probiotic, may inhibit the infection caused by Vibrio anguillarum through stimulating Caenorhabditis elegans to secrete antibacterial effectors and detoxification proteins. This paper provides a new direction for screening marine probiotics and an experimental basis to support the potential application of ML1206 as a marine probiotic in aquaculture.

Male reproductive toxicity involved in spermatogenesis induced by perfluorooctane sulfonate and perfluorooctanoic acid in Caenorhabditis elegans

As a persistent organic pollutant, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have gained increasing research attention over recent years because of their potential risk to humans and the environment. In this paper, we investigated the reproductive toxicity of these pollutants using a C. elegans model to evaluate spermatogenesis throughout the entire developmental cycle of him-5 mutant by exposing to 0.001, 0.01, and 0.1 mmol/L PFOS or PFOA for 48 h. Experimental results suggested that PFOS and PFOA exposure led to reductions in brood size, germ cell number, spermatid size, and motility, and increases in rate of malformation spermatids. Analysis of variance (ANOVA) showed that exposure to PFOS resulted in higher levels of damage than PFOA in germ cells only in 0.001 mmol/L exposure group. RT-qPCR was used to further investigate the expression of genes associated with different stages of spermatogenesis, such as mitosis and meiosis, fibrous body-membranous organelles (FB-MOs), and sperm activation. The expression levels of wee-1.3, spe-4, spe-6, and spe-17 genes were increased, while those of puf-8, spe-10, fer-1, swm-1, try-5, and spe-15 genes were decreased. Our results suggesting that PFOS or PFOA may cause spermatogenesis damage by disrupting the mitotic proliferation, meiotic entry, formation of the MOs, fusion of the MOs and plasma membrane (PM), and pseudopods. Loss-of-function studies using puf-8 and spe-10 mutants revealed spe-10 gene was specifically involved in PFOS- or PFOA-induced reproductive toxicity via regulating one or more critical palmitoylation events, while puf-8 gene was not direct target of PFOS and PFOA, and PFOS and PFOA may act on the upstream gene of puf-8, thus affecting reproductive ability. Taken together, these results demonstrate the potential adverse impact of PFOS and PFOA exposure on spermatogenesis and provide valuable data for PFC risk assessment. Grapical abstract.

Bacterial degradation of distillery wastewater pollutants and their metabolites characterization and its toxicity evaluation by using Caenorhabditis elegans as terrestrial test models

Distillery wastewater has significant amount of coloring compounds and organic substances even after the secondary treatment process, which poses many severe environmental and health threats. However, the recalcitrant coloured compounds have not yet been clearly identified. In this study, two bacterial strains DS3 and DS5 capable to decolorize distillery wastewater (DWW) pollutants were isolated and characterized as Staphylococcus saprophyticus (MF182113) and Alcaligenaceae sp. (MF182114), respectively. Results showed that mixed bacterial culture was found more effective decolorizing 71.83% DWW compared to axenic culture DS3 and DS5 resulting only 47.94% and 50.67% decolorization, respectively. The FT-IR and LC-MS/MS analysis of untreated DWW showed the presence of many recalcitrant compounds having different functional groups, but after bacterial treatment, most of compounds get diminished and the toxicity of DWW was reduced significantly. Further, the Nile red staining of Caenorhabditis elegans exposed to untreated and bacteria treated DWW for evaluation of toxicity assay and results revealed that the worms exposed to untreated DWW showed sharp reduction in total fat content having more profound effects, suggesting the diminished nAchR signaling as compare to bacterial treated DWW. Hence, this study revealed that inadequate disposal of untreated DWW may cause transfer of toxic substances into the environment and receiving water bodies.

Ecotoxicological effects of micropollutant-loaded powdered activated carbon emitted from wastewater treatment plants on Daphnia magna

In order to eliminate micropollutants from wastewater, the use of powdered activated carbon (PAC) is a suitable and common technique. Many studies already proved the successful elimination of micropollutants from wastewater using PAC. However, it still remains a challenge to completely retain the applied PAC within the wastewater treatment plant (WWTP) without considerable emission of PAC into receiving waters. The present study investigates possible toxic effects of micropollutant-loaded PAC from a WWTP in acute and chronic tests with the aquatic organism Daphnia magna. Furthermore, the well-studied micropollutant diclofenac as well as unloaded, native PAC and experimentally diclofenac-loaded PAC were tested. The acute tests resulted in median effect concentrations (EC₅₀) after 48 h of 53 mg/L for diclofenac, 217 mg/L for native PAC and 414 mg/L for diclofenac-loaded PAC. No effects were detected for the loaded PAC from the WWTP although D. magna ingested the PAC. The chronic tests revealed that diclofenac had effects on growth, reproduction and mortality (median lethal concentration 17.0 mg/L). Exposure to native and diclofenac-loaded PAC showed clear effects on growth and a reproduction inhibition of 80% in the highest tested concentrations. The calculated reproduction EC₁₀ values were 0.8 mg/L for native PAC and 0.3 mg/L for diclofenac-loaded PAC. For the loaded PAC from the WWTP, no effects were observed on reproduction, growth and mortality during the 21-day exposure albeit the fact that the animals ingested the PAC into their gastrointestinal system. Based on these findings PAC from WWTP can be considered as not harmful to D. magna even if complete retention of the PAC at the WWTP cannot be guaranteed.

Investigation and assessment of micropollutants and associated biological effects in wastewater treatment processes

Currently, the wastewater treatment plants (WWTPs) attempt to achieve the shifting from general pollution parameters control to reduction of organic micropollutants discharge. However, they have not been able to satisfy the increasing ecological safety needs. In this study, the removal of micropollutants was investigated, and the ecological safety was assessed for a local WWTP. Although the total concentration of 31 micropollutants detected was reduced by 83% using the traditional biological treatment processes, the results did not reflect chemicals that had poor removal efficiencies and low concentrations. Of the five categories of micropollutants, herbicides, insecticides, and bactericides were difficult to remove, pharmaceuticals and UV filters were effectively eliminated. The specific photosynthesis inhibition effect and non-specific bioluminescence inhibition effect from wastewater were detected and evaluated using hazardous concentration where 5% of aquatic organisms are affected. The photosynthesis inhibition effect from wastewater in the WWTP was negligible, even the untreated raw wastewater. However, the bioluminescence inhibition effect from wastewater which was defined as the priority biological effect, posed potential ecological risk. To decrease non-specific biological effects, especially of macromolecular dissolved organic matter, overall pollutant reduction strategy is necessary. Meanwhile, the ozonation process was used to further decrease the bioluminescence inhibition effects from the secondary effluent; ≥ 0.34 g O₃/g DOC of ozone dose was recommended for micropollutants elimination control and ecological safety.

Zebrafish CYP1A expression in transgenic Caenorhabditis elegans protects from exposures to benzo[a]pyrene and a complex polycyclic aromatic hydrocarbon mixture

Polycyclic aromatic hydrocarbons (PAHs) are environmental toxicants primarily produced during incomplete combustion; some are carcinogens. PAHs can be safely metabolized or, paradoxically, bioactivated via specific cytochrome P450 (CYP) enzymes to more reactive metabolites, some of which can damage DNA and proteins. Among the CYP isoforms implicated in PAH metabolism, CYP1A enzymes have been reported to both sensitize and protect from PAH toxicity. To clarify the role of CYP1A in PAH toxicity, we generated transgenic Caenorhabditis elegans that express CYP1A at a basal (but not inducible) level. Because this species does not normally express any CYP1 family enzyme, this approach permitted a test of the role of basally expressed CYP1A in PAH toxicity. We exposed C. elegans at different life stages to either the PAH benzo[a]pyrene (BaP) alone, or a real-world mixture dominated by PAHs extracted from the sediment of a highly contaminated site on the Elizabeth River (VA, USA). This site, the former Atlantic Wood Industries, was declared a Superfund site due to coal tar creosote contamination that caused very high levels (in the [mg/mL] range) of high molecular weight PAHs within the sediments. We demonstrate that CYP1A protects against BaP-induced growth delay, reproductive toxicity, and reduction of steady state ATP levels. Lack of sensitivity of a DNA repair (Nucleotide Excision Repair)-deficient strain suggested that CYP1A did not produce significant levels of DNA-reactive metabolites from BaP. The protective effects of CYP1A in Elizabeth River sediment extract (ERSE)-exposed nematodes were less pronounced than those seen in BaP-exposed nematodes; CYP1A expression protected against ERSE-induced reduction of steady-state ATP levels, but not other outcomes of exposure to sediment extracts. Overall, we find that in C. elegans, a basal level of CYP1A activity is protective against the examined PAH exposures.

Systematic Review of Toxicity Removal by Advanced Wastewater Treatment Technologies via Ozonation and Activated Carbon

Upgrading wastewater treatment plants (WWTPs) with advanced technologies is one key strategy to reduce micropollutant emissions. Given the complex chemical composition of wastewater, toxicity removal is an integral parameter to assess the performance of WWTPs. Thus, the goal of this systematic review is to evaluate how effectively ozonation and activated carbon remove in vitro and in vivo toxicity. Out of 2464 publications, we extracted 46 relevant studies conducted at 22 pilot or full-scale WWTPs. We performed a quantitative and qualitative evaluation of in vitro (100 assays) and in vivo data (20 species), respectively. Data is more abundant on ozonation (573 data points) than on an activated carbon treatment (162 data points), and certain in vitro end points (especially estrogenicity) and in vivo models (e.g., daphnids) dominate. The literature shows that while a conventional treatment effectively reduces toxicity, residual effects in the effluents may represent a risk to the receiving ecosystem on the basis of effect-based trigger values. In general, an upgrade to ozonation or activated carbon treatment will significantly increase toxicity removal with similar performance. Nevertheless, ozonation generates toxic transformation products that can be removed by a post-treatment. By assessing the growing body of effect-based studies, we identify sensitive and underrepresented end points and species and provide guidance for future research.